The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2001-365941, filed on Nov. 30, 2001, the contents of which is herein expressly incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a battery power source device including a plurality of battery pack blocks, each of which is constituted by connecting a plurality of rechargeable batteries in series, and battery ECUs for controlling the operation state of the battery pack blocks. The plurality of battery pack blocks are connected with one another in parallel or by a combination of serial connection and parallel connection (in series-parallel). The invention also relates to a current detection method therefor.
2. Description of Related Art
A battery power source device applied as a power source for an electric vehicle or hybrid car must supply large electric power. The device is therefore configured as a battery pack system. In the system, a plurality of (six for example) rechargeable batteries are connected together in series to constitute a battery module, and a plurality of (30 for example) such battery modules are connected together in series to constitute a battery pack block. A battery ECU (Electronic Control Unit) is also provided in order to control the operation state of the battery pack block. The battery ECU detects the voltage, current, and temperature of each battery pack block and carry out abnormality detection and various control based on the detection results. To meet a demand for significantly large power for a large-sized vehicle, for example, connecting such battery pack systems together in series, parallel or in series-parallel has been considered.
FIG. 3 is a diagram showing the configuration of a battery power source device having six battery pack systems connected together in series-parallel. The battery pack systems all have the same arrangement including a battery pack block 21 and a battery ECU 22. The battery pack blocks 21 connected in series-parallel are each connected with a positive electrode charge/discharge terminal 23 and a negative electrode charge/discharge terminal 24. The operation state of each of the battery pack blocks 21 is monitored and controlled by the corresponding battery ECU 22.
The battery pack block 21 is provided with sensors to detect voltage per battery module, charge/discharge current to/from the battery pack block 21, battery temperature per battery module, and the ambient temperature of the battery pack block 21, and the detection outputs of the sensors are input to the corresponding battery ECU 22. The battery ECU 22 monitors the operation state or abnormality of the battery pack block 21 based on the input voltage, current, and temperature detection outputs. Meanwhile, the battery ECU 22 controls a cooling device such as a blower fan provided at the battery pack block 21 based on the temperature detection output. The battery ECU 22 also calculates SOC (State Of Charge: accumulated electrical quantity relative to battery capacity) based on the voltage, current, and temperature detection outputs. The SOC and the detection output such as voltage are externally output as the operation state data of the battery pack block 21, so as to be input to a vehicle ECU in a hybrid car for example and used for controlling charge/discharge to/from the battery power source device.
For example in a hybrid car using the battery power source device having a plurality of battery pack blocks connected in series-parallel as described above as the power source, there is a request that the total charge/discharge current I in the battery power source device be known.
The total charge/discharge current I can be detected by a special current sensor for high current provided at a charge/discharge circuit connected with the positive electrode charge/discharge terminal 23 or the negative electrode charge/discharge terminal 24 of the battery power source device. However, not only the expensive current sensor is necessary, but also a processing circuit for processing and amplifying the detection output of the current sensor is necessary, which increases the cost.
Meanwhile, the battery pack blocks 21 are each provided with a current sensor 25, and the charge/discharge current is separately detected for each battery pack block 21 by the corresponding battery ECU 22. Consequently, when the charge/discharge current values at the battery pack blocks 21 connected in parallel are added up, the total charge/discharge current I should be produced. However, the detected current is used to calculate the SOC as described above. Thus, as shown in FIG. 4, once the current is input to the battery ECU 22, it is amplified by an amplification circuit 16, then A/D-converted by an A/D conversion circuit 17, and input to a microcomputer 18 for digital processing. The A/D-converted current data cannot be in synchronization with each other among the battery pack systems A1 to A6, and it is therefore impossible to produce the total charge/discharge current I simply by adding them up.
It is an object of the present invention to provide a battery power source device that allows the total charge/discharge current to be obtained using the current detection function provided at each of a plurality of battery pack blocks, and a current detection method therefor.
In order to achieve the above object, a first aspect of the present invention is directed to a method for detecting a total charge/discharge current in a battery power source device. The battery power source device includes a plurality of battery pack systems connected in parallel or series-parallel. Each of the battery pack systems includes: a battery pack block having a plurality of rechargeable batteries connected in series; a battery ECU that detects a current, a voltage, and a temperature and controls an operation state of the battery pack block based on the detection result; and a charge/discharge circuit for connecting the battery pack block. The method for detecting a total charge/discharge current includes: detecting currents at the respective charge/discharge circuits of the battery pack systems detected by the corresponding battery ECUs provided at the battery pack systems connected in parallel; and adding up the currents in an analog data state.
According to the current detection method, the total charge/discharge current in the battery power source device is obtained without having to provide current detection means and a processing circuit. Current data after A/D conversion may not accurately be added, while analog data before A/D conversion are accurately added. Consequently, charge/discharge currents detected by the battery ECUs in the battery pack systems connected in parallel can be added up to obtain the total charge/discharge current in the battery power source device.
A second aspect of the invention is directed to a battery power source device, comprising a plurality of battery pack systems connected in parallel or series-parallel. The battery pack systems each includes: a battery pack block having a plurality of rechargeable batteries connected in series; a battery ECU for detecting a current, a voltage, and a temperature and for controlling an operation state of the battery pack block based on the detection result; and a charge/discharge circuit for connecting the battery pack block, the circuit including a current sensor. The battery ECU includes an amplification circuit for processing and amplifying a current detection output from the current sensor, and an A/D conversion circuit for receiving and A/D-converting an output value from the amplification circuit for output as a detection value for the current to be used for controlling an operation state of the battery pack system. The power source device further includes an addition unit for adding up the output values of the amplification circuits of the battery ECUs in the battery pack blocks connected in parallel to detect the total charge/discharge current value.
When the output values in the amplification circuits of the battery ECUs in the battery pack systems connected in parallel are added up, the total charge/discharge current in the battery power source device is obtained.
In the above-described configuration, the addition unit collects and adds up the output values of the amplification circuits of the battery ECUs provided at the battery pack systems connected in parallel. The addition unit is provided as an addition circuit at each of the battery ECUs, and an arbitrary one of the battery ECUs serves as a master and the output values of the amplification circuits in the other battery ECUs serving as slaves are input to the addition circuit in the master battery ECU for addition. Thereby, all the battery ECUs can have the same arrangement. In this way, the production management is efficient and the output values are collected to the addition unit in the master battery ECU by the interconnection.
The master battery ECU A/D-converts the total charge/discharge current value produced by the addition by the addition circuit to be used as management data for the operation state. The total charge/discharge current data can be provided to equipment that uses the battery power source device.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.